This invention relates to the construction of pipelines, i.e., sewer and water pipelines of the type used by municipalities, for example, and particularly to systems for laying stone beds in the bottom of trenches which are frequently dug in flowable, sandy soil which includes sand and water bearing strata where flooding-in and cascading-in of the sides of the trench is an ever-present problem. Typically, if wellpoint-pumping does not sufficiently dewater the area in which the trench is to be dug, stone is manually spread in the bottom of such trenches after they are dug, and the procedure is arduous, time-consuming and expensive. The stone beds formed in the bottom of the trench by such methods have resulted in non-uniform beds, in some places excessively thick and therefore unduly costly, and in other places insufficient to properly support the pipeline. Moreover, several crews of workmen are required under present practice to first do the dewatering and then afterward to lay the stone bed and pipeline.
One of the prime objects of the present invention is to provide a stone-laying box capable of simultaneously laying a stone bed with higher level packed side walls which shore up the bottom side walls of the trench, while at the same time, pumping water out of the trench and pushing cascaded sandy ground which has fallen into the trench ahead of the box so that it can be removed by the backhoe or other trenching vehicle being used to dig the trench, and to move the trench box along the trench incrementally while the trench is being dug.
A further object of the invention is to lay a pipe-accommodating bed of the character described which is packed into a predesignated contour by the very act of the stone box being pushed along the bottom of the trench.
Still another object of the invention is to provide a pipe bed laying system adequate to support the pipeline.
Another object of the invention is to provide a pipe bed laying system which operates expeditiously and efficiently to accomplish the job in a far more satisfactory and economical manner than heretofore has been possible.